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    SubjectRe: [PATCH 4/6] drivers:misc: sources for Init manager module
    --- On Wed, 24/3/10, Marcel Holtmann <marcel@holtmann.org> wrote:

    > From: Marcel Holtmann <marcel@holtmann.org>
    > Subject: Re: [PATCH 4/6] drivers:misc: sources for Init manager module
    > To: "Pavan Savoy" <pavan_savoy@yahoo.co.in>
    > Cc: "Greg KH" <gregkh@suse.de>, "PavanSavoy" <pavan_savoy@ti.com>, "alan@lxorguk.ukuu.org.uk" <alan@lxorguk.ukuu.org.uk>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
    > Date: Wednesday, 24 March, 2010, 9:41 PM
    > Hi Pavan,
    >
    >
    > > I wanted to somehow put this in staging because then
    > it would probably have a thorough architectural review
    > process.
    > > Some details about this driver -
    > >
    > > 1. This driver will be used by Bluetooth-BlueZ/FM-V4L2
    > and GPS (probably character device driver) using the
    > EXPORTED symbols (-register/_unregister).
    > >
    > > 2. Much like the hciattach daemon which maintains
    > N_HCI bluetooth line discipline, this driver will also have
    > a User-Space  N_TI_WL Init manager (UIM) maintaining
    > the Line discipline.
    >
    > can you explain why you think this is needed and we can not
    > interface
    > this directly. If it is a serial port, what protocol does
    > it talk?

    Illustration: The BT driver on top of this ST driver, would create a hci0 interface, when someone does an DEVUP on that interface, the BT driver would then do a st-register - which in-turn would ask the hciattach-like daemon to install the line discipline for it via the sysfs entry.
    The same concept goes for FM-V4L2 and GPS character driver.

    The core of the problem is we cannot ask/install/ldisc_put for a line discipline from kernel space.

    >
    > > 3. Because of the UIM should know when to
    > install/uninstall line discipline, the /sys entry is created
    > a root called UIM (a new kobject) and UIM daemon would write
    > it's PID to it.
    >
    > I don't understand this. This sounds like a broken concept
    > to me.

    Yes, I don't feel good about it either. But how do I request for a line discipline from kernel space ?
    Currently a daemon has to run in user-space to maintain the ldisc, at all times, and I don't want to open TTY @ boot, and install Ldisc (tiocsetd) on it, without BT/FM or GPS core on chip being used - The Power Management team here would beat me up if I do that,
    and hence the very dumb idea of passing the PID of the daemon via sysfs entry, and the driver sending SIGUSR2 to that PID, daemon doing a tiocsetd upon that signal.

    >
    > > 4. As Alan suggested, If I make it self-contained by
    > pushing number of line disciplines to a slightly larger
    > number, then would it be OK ?
    >
    > Just from a quick look, I think within a few review cycles
    > this might be
    > able to get proper upstream inclusion. No idea why bother
    > with staging
    > in the first place. Lets do this correctly.
    >

    The only reason I wanted this to be in staging was to have sort of continuous review process, and in hope the driver wouldn't be forgotten.

    > Regards
    >
    > Marcel
    >
    >
    >


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